A few lessons from Sherlock Holmes | Peter Bevelin


Published: 2013
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Peter Bevelin is the author of the books Seeking wisdom: From Darwin to Munger, A few lessons for investors and managers and All I want to know is where I’m going to die so I’ll never go there. In this particular book, inspired by Arthur Conan Doyle’s famous Sherlock Holmes books, Bevelin has collected principles and tricks used by the fictional detective to think more clearly. Even though the character is fictional, the models and tricks work in many areas of life – not just when a crime is to be solved.  

THE MIND IS LAKE AN ATTIC. Sherlock Holmes partner Dr. Watson is described to be amazed at how Sherlock can be brilliant in certain areas and at the same time have large knowledge gaps in other basic areas. Sherlock, however, compares a person’s brain with an empty little attic. Only a fool fills this attic with debris of all kinds. A wise person fills the attic with carefully selected furniture. The attic, just like the brain, has limited space and for every bad piece of furniture you take in, a good piece of furniture needs to go out.

SYSTEMATIZE COMMON SENSE. There is no rule on how to think. However, it is possible to formulate certain principles, since the art of thinking clearly is based on an ability to systematize common sense. Like all art forms, a good inference and analysis ability can only be acquired through long-term and patient studies. The education never ends. Gather facts, create a hypothesis, test it and seek verification. And always have an open mind.

LEARN FROM HISTORY. One recommendation on how to develop your ability to solve crimes is to lock yourself in for three days and read 12 hours a day about historical crimes. Most things go in circles and by understanding historical patterns, we can improve the ability to assess probabilities of outcome.

NEVER DRAW HASTY CONCLUSIONS. There are psychological biases, “inefficient” mental habits and connections from the evolution, which cause people to systematically draw the wrong conclusions. In some cases, it is a habit and in other cases we are incorrectly trained. As the saying goes: ”Men see a little, presume a good deal, and so jump to the conclusion”.

”It is evident that if the first stage – the collection of the facts – is improperly done, we have not the basis for the second and it is bound to be wrong. The game is hopelessly lost from the start. How important, therefore, to give every effort to the collection of our facts”

AVOID CONFIRMATION BIAS. The human tendency to draw hasty conclusions often leads to an unfair collection of evidence. A common denominator for mediocre detectives is that they have often decided what has happened – then they gather evidence that confirms this and make sure that the facts fit into the theory. Holmes prefers to first gather facts and then carefully make observations and conclusions until he is irresistibly drawn in one direction – even if he had not originally intended to go in that direction.

“When we meet a fact which contradicts a prevailing theory, we must accept the fact and abandon the theory, even when the theory is supported by great names and generally accepted”

THE MISSING PIECE. Instead of looking for clues, it can sometimes be wise to stop and think about what is missing. The world is full of obvious things that no one observes. Holmes attributes his success to the fact that he trained himself to see what others are missing (sometimes formulated as ”not invisible but unnoticed, Watson” and “once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth”).

“Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth”

PATTERN RECOGNITION. There is no standard method of inference that always works for all people. A person can act in a way that is representative of society at large but that differs from the person’s normal behavioral patterns. This can be a clue in that specific case.

 “All the time that she was telling me this story she never once looked in my direction, and her voice was quite unlike her usual tones. It was evident to me that she was saying what was false. I said nothing in reply, but turned my face to the wall, sick at heart, with my mind filed with a thousand venomous doubts and suspicions. What was it that my wife was concealing from me? We must look for consistency. Where there is a want of it we must suspect deception”

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